A bad universal joint in a vehicle is detected by looking out for signs such as dust and excessive vibration in the prop-shaft. The U-joint cannot be dismantled in most current car models, as it is permanently joined to the prop-shaft, thus requiring the entire shaft to be changed.Continue Reading
Excessive vibration in the prop-shaft is one indicator of a worn U-joint. Depending on the car model, the joint is lubricated or replaced, or the prop-shaft is replaced entirely.
A clonking sound when accelerating or decelerating is another indicator of a bad joint. A regular knock when the car is in motion is also an indicator of a bad joint.
There should be no play in the joint if it is in good condition. To check the condition of a U-joint, firmly grip one side of the joint and try to turn the other side. The joint should hold firmly if it is in good condition. Alternatively, insert a large screwdriver between the levering and yoke to see if there is any play. A new joint or prop-shaft needs to be fitted if any play is detected.
The presence of rust-colored dust around the spider is an indication of a faulty U-joint. Put in a new shaft or joint immediately when dust is detected around the spider.